Effects Of Three Doses Of Dexmedetomidine On Routine Electrocardiogram In Patients Undergoing Orthopaedic Surgery

Objective To investigate the effect of single pump with different doses of dexmedetomidine on routine electrocardiogram in patients undergoing orthopaedic surgery.Methods Eighty male patients with orthopedic surgery,aged 20-65 years,body mass index<30 kg/m²,ASA physical status?or?,had no history of hypertension,coronary heart disease,diabetes mellitus,electrolyte disturbance,and no drug that affected QT interval.,ECG showed no sinus bradycardia,sinus tachycardia and atrioventricular block,QTc<440 ms,were randomly divided into group D1,D2,D3and C with 20 each.All patients were fasted for 10 hours before operation,and no preoperative drugs were used.After entering the operating room,the venous passage was established,and the ECG was monitored.The patients were ordered to lie quietly and prone for 10 minutes,and the oxygen 2 L/min was given by nasal catheter.Dexmedetomidine 200?g was diluted to 50 ml.Group D1,D2 and D3 were infused with dexmedetomidine 0.3 ug/kg,0.5 ug/kg and 0.8 ug/kg using a micro-pump for 10min,group C infused 0.9%NaCl solution in the same manner.Patients whose heart rate slower than 45 times/minute were eliminated.MAP,HR,SpO₂ were recorded and ECG was traced at the time before injection?T₁?,5 min?T₂?,10 min?T₃?after injection and 10min after the end of pumping?T₄?.P wave duration,P-R interval,QRS time,and QTc value were calculated.The occurrence of adverse reactions such as respiratory depression,hypotension,bradycardia and malignant arrhythmia were recorded.Results1.Comparison of general data There was no significant difference in age and BMI between the four groups.2.Comparison of MAP,HR and SpO2 Compared with T1 time point and C group,MAP was significantly decreased,HR was significantly slowed down in group D2 and D3 from T₂ to T₄?P<0.05?.There was no significant difference in MAP and HR at each time point in group C and group D1.All patients in four groups have SpO2 of 100%.3.Comparison of P wave duration,P-R interval,QRS time limit and QTc value Compared with those at T1 time point and C group,QTc values of D2 and D3groups were significantly shortened at T2^T4?P<0.05?.There was no significant difference in QTc value between group C and group D1 at different time points.There was no significant difference in the P wave duration,P-R interval and QRS duration among the four groups at different time points.4.Comparison of adverse reactions There was no severe hypotension or bradycardia requiring correction in the four groups.No respiratory depression,arrhythmia and so on.Conclusion1.The intra-atrial,atrioventricular and intra-ventricular conduction of routine electrocardiogram in patients undergoing orthopaedic surgery was not affected by dexmedetomidine at 0.3 ug/kg,0.5 ug/kg and 0.8 ug/kg.The QT interval was shortened by dexmedetomidine at 0.5 ug/kg and 0.8 ug/kg.2.To avoid severe bradycardia,patients with low heart rate may be used no more than 0.5?g/kg dexmedetomidine.